This invention relates to a heat transfer device which is suitable for the flowing-through of several fluids and has a construction of several plates which are stacked above one another and are provided with openings.
Heat transfer devices of this type are described, for example, in German Patent Document DE 32 06 397 C2. There, plates of a same type, which are each provided with parallel rows of oblong openings, are stacked on one another in such a manner that the openings of one plate are in a fluid connection with adjacent openings of the same row of an adjoining plate. In this manner, each group of superimposed rows of openings forms a two-dimensional flow duct network, the network planes being situated in parallel to the stacking direction and the individual networks having no fluid connection with one another within the stack. By means of suitable inflow and outflow devices on the sides of the stack toward which the networks are open, the individual networks can be divided into several groups, a specific fluid flowing through each of them.
From German Patent Document DE 37 09 278 C2, a heat transfer device having a plate stack construction is known in the case of which the plates, which are stacked upon one another, are provided on one of the two flat sides with longitudinal grooves which are situated side-by-side and which are used as flow ducts. During the stacking, as required, adjacent plates are then arranged to be tilted with the same orientation by 180.degree. with respect to one another or are arranged to be rotated by 90.degree. with respect to one another, whereby co-current flow or countercurrent flow arrangements with a larger or smaller duct cross-section or crosscurrent flow arrangements are formed.
In the applicant's German Patent Application 195 28 117.9 (corresponding U.S. application filed Aug. 1, 1996 under Ser. No. 08/691,897, now U.S. Pat. No. 5,718,286) which is no prior publication, a heat transfer device of the initially mentioned type is described in the case of which a plate stack construction is provided which consists of flow duct plate units and connection cover plate units which are alternately stacked on one another. The flow duct plate units are provided with flow duct openings extending between two lateral areas as well as with connection duct openings separated therefrom, while in the connection cover plate units, connection duct openings on at least two lateral areas are provided in such a manner that they suitably overlap with respective equal-sided ends of the flow duct openings of an adjoining flow duct plate unit as well as a connection duct opening of the flow duct plate unit adjoining on the other side. As a result, two separate flow duct systems are formed through which two fluids can flow, depending on the mutual orientation of flow duct plate units following one another in the stack, in the crosscurrent, the countercurrent or the co-current transversely to the stack direction.
For certain applications, there is a demand for heat transfer devices by means of which, by means of a thermal interaction with a working fluid, a fluid can be tempered, that is, cooled or heated beyond a desired temperature value, and can subsequently be brought to the desired temperature by means of the thermal interaction with the fluid flow existing in front of the heat transfer area of the working fluid. Thus, for example, high temperature batteries for driving electric vehicles typically have a working temperature of approximately 300.degree. C., in which case the temperature continues to rise in phases of a high current consumption because of internal losses. For preventing damage, the battery must be cooled, for the purpose of which, as a rule, silicone fluid is circulated as the heat transfer medium through the battery. By means of an oil/water heat transfer is device outside the battery, the oil is recooled, in which case, for reasons of space, heat transfer devices are desired which are as compact as possible. The silicone fluid must now, on the one hand, be cooled to a temperature which is compatible with an assigned fluid pump; on the other hand, the fluid must not be returned to the battery at such a low temperature because otherwise, additionally, thermal energy must be generated in the interior of the battery with the result of a loss of electric energy and therefore of vehicle range. A heat transfer device is therefore required by means of which heat is first withdrawn from the fluid coming out of the battery until it reaches a pump-compatible temperature, and by means of which, the fluid, after flowing through the pump, is heated again to a desirable battery inlet temperature.
The invention is based on the technical problem of providing a heat transfer device of the initially mentioned type which can be produced and mounted at relatively low expenditures, has a high heat transfer output in the existing required space and is suitable particularly for applications in which, as in the above-described case of a high-temperature battery cooling, a fluid is to be cooled or heated by a working fluid beyond a desired temperature value and subsequently is to be brought to the desired temperature value by the thermal interaction with the fluid flow existing in front of the working fluid.
This problem is solved according to certain preferred embodiments of the invention by means of a heat transfer device having a construction consisting of several plates which are stacked above one another and have openings, comprising at least one first and at least one second flow duct plate unit, of which the first flow duct plate unit is provided with a group of side-by-side flow duct openings which extend between two plate side areas, and the second flow duct plate unit is provided with two separate groups of side-by-side flow duct openings which extend between two plate side areas, the first and the second flow duct plate units being arranged in an alternating manner in a plate stack and having connection duct openings which are separate from the flow duct openings, and at least one connection cover plate unit arranged between two flow duct plate units respectively while covering flow duct openings of the flow duct plate units with respect to one another and having connection plate unit flow duct openings, wherein the connection duct openings in the flow duct plate units and in the at least one connection cover plate unit for forming one distributor and collector duct pair respectively for each of the three groups of side-by-side flow duct openings are arranged such that a first pair of connection duct openings of a respective connection cover plate unit overlaps, on the one hand, with a first pair of corresponding connection duct openings of an adjoining first flow duct plate unit and, on the other hand, with the respective ends of the corresponding one group of flow duct openings of an adjoining second flow duct plate unit, a second pair of connection duct openings of the connection cover plate unit overlaps, on the one hand, with a second pair of corresponding connection duct openings of the first flow duct plate unit and, on the other hand, with respective ends of the corresponding other group of flow duct openings of the second flow duct plate unit, and a third pair of connection duct openings of the connection cover plate unit overlaps, on the one hand, with a pair of corresponding connection duct openings of the second flow duct plate unit and, on the other hand, with respective ends of the group of flow duct openings of the first flow duct plate unit.
For implementing the plate stack construction of this heat transfer device, plate units are only required which are provided with suitable openings which can be produced at low expenditures, for example, by means of stamping, eroding, laser beam or water jet cutting. The flow duct openings of the flow duct plate units form the heat-exchange-active flow ducts which extend perpendicularly to the stacking direction and are each bounded by adjacent connection cover plate units. In addition to this flow duct cover function, the connection cover plate units simultaneously carry out a connecting function which includes, by means of corresponding connection duct openings, in each case, the providing of a fluid connection for the equal-sided ends of the flow duct openings of a respective flow duct plate unit with respect to one another. By way of additional, appropriately overlapping connection duct openings of adjoining plate units, specifically of connection cover plate units as well as of flow duct plate units, in addition, in each case, the equal-sided ends of the flow duct openings of the next but one flow duct plate units are in a fluid connection with one another.
By means of the use of two different types of flow duct plate units alternating in the stack, up to three fluid flows can be guided separately from one another through the very compactly constructed heat transfer device, specifically a first fluid by way of the group of the flow duct openings of one or several first flow duct plate units; a second fluid by way of one of the two groups of flow duct openings of one or several second flow duct plate units; and a third fluid by way of its other group of flow duct openings. The fluid flow guided through the at least one first flow duct plate unit is preferably situated in the crosscurrent to the two fluid flows guided through the at least one second flow duct plate unit. By means of a corresponding external connecting of a fluid outlet side of one of the groups of flow duct openings with a fluid inlet side of another group, the heat transfer device is particularly suitable for the guiding through of two fluids while returning the one fluid guided once through a group of flow duct openings into the plate stack for the purpose of another thermal interaction with at least one of the two fluid flows passing through the other groups of flow duct openings. By way of the length of the plate units in the longitudinal direction of the flow duct openings, the effective heat exchange length can be set, and, by way of the number of plate units stacked above one another, the effective flow cross-section for the respective fluid flow can be adjusted. A suitable structuring and stacking of the flow duct plate units and of the connection cover plate units permits, in addition to the implementation of crosscurrent heat transfer devices also the implementation of countercurrent and co-current heat transfer devices of this type.
In the case of certain preferred embodiments of the invention, a fluid flow sent through the flow duct openings of the first flow duct plate units can thermally interact successively first with a fluid flow guided through the first group of flow duct openings of the second flow duct plate units and subsequently with a fluid flow guided through its second group of flow duct openings, while no significant thermal interaction exists between the two separate fluid flows in the second flow duct plate units.
In certain preferred embodiments, a fluid entering by way of the distributor duct of the first flow duct plate units can be tempered by a fluid guided through one group of flow duct openings of the second flow duct plate units and subsequently, for the purpose of a thermal interaction with its own, still not yet tempered fluid flow, can again be sent through the heat transfer device plate stack in order to compensate a previously occurred excess tempering. This heat transfer device is particularly well suited for the above-described special case of a high-temperature battery cooling in which the battery fluid, for the purpose of being guided through a pump, must first be cooled beyond the desired extent and must then be slightly heated again.
The placing of insulating slot openings provided in a further development of the invention permits a reduction of the wall temperature of the heat transfer device plate stack in the corresponding area and particularly, in the case of the use as a cooling element, a reduction of the heat losses.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.